Two developmental conditions in which abnormal binocular interactions play an important role will be investigated in detail: monocular deprivation and strabismus. In the case of monocular deprivation, single cell neurophysiological experiments will be conducted in striate cortex to learn more about the nature of the binocular interactions which occur during the course of development. In addition, the mechanisms by which the effects of monocular deprivation are produced and maintained in the visual system will be investigated. Previous studies from this laboratory and elsewhere have shown that if the influence of the experienced eye is removed after the critical period, some of the morphological and neurophysiological effects of monocular deprivation can be reversed. This finding has implications for understanding the mechanisms of the abnormalities which occur with monocular deprivation, and will be investigated further. Anatomical studies will be carried out to determine if the projections from the deprived eye change with the reversal. Neurophysiological experiments will be conducted in both the lateral geniculate and striate cortex to learn more about the functional properties of the reversal, and the relationship between anatomical and physiological changes in both structures. Behavioral experiments will investigate the significance of these changes for the visual abilities of the animal. Finally, additional neurophysiological experiments will investigate the location and pharmacological mechanisms of the abnormal binocular interactions which are present following rearing with monocular deprivation. A related series of experiments will be conducted which will extend this analysis to the effects of rearing with strabismus. Single cell recording will be conducted in striate cortex to compare the effects of convergent and divergent strabismus, to determine if the effects differ in the two hemispheres, and to compare the effects in different regions of the visual field representation within striate cortex. Additional neurophysiological experiments will investigate the mechanisms of the abnormalities produced by rearing with strabismus and assess the extent to which they are produced by interocular suppression.